Method and apparatus for analyzing a gas sample

An mass spectrometer system comprising:

• an ion pump for creating a vacuum within said mass spectrometer;
• an ionization chamber with a first and a second orifice;
• an inlet passage through which a gas sample is introduced into said ionization chamber;
• valve means associated with the inlet passage for controlling the volume of gas sample introduced into said ionization chamber;
• a filament for introducing electrons into said ionization chamber via the first orifice whereby the electrons bombard the gas sample thus forming ions;
• a first magnet positioned for producing a magnetic field within said ionization chamber which serves to focus the electrons into a beam within said ionization chamber;
• a collector positioned adjacent said first orifice, said collector being biased more negative than said filament such that said collector is operative to focus the electrons emitted from said filament and further operative to collect ions leaving said ionization chamber via said first orifice;
• a filter chamber;
• an extractor plate adjacent said second orifice of said ionization chamber, said extractor plate being biased such that a proportion of ions and electrons in said ionization chamber are allowed to pass into said filter chamber;
• a quadrupole filter in said filter chamber through which the emitted ions and electrons are directed by said extractor plate, said quadrupole filter allows ions of only a selected mass-to-charge ratio to pass through said quadrupole filter;
• a second magnet for attracting electrons toward the ions other than those having the selected mass-to-charge ratio in the area of said quadrupole filter so that the electrons combine with the ions;
• a third magnet for collecting electrons that did not combine with any ion in the area of said quadrupole filter;
• a separator plate for focusing the ions of the selected mass-to-charge ratio after the ions have passed through said quadrupole filter;
• a sensor for receiving the ions that have been focused by said separator plate;
• and
• analyzing means connected with said sensor for analyzing the components of the gas sample.

A mass spectrometer system comprising:

• means for creating a vacuum envelope within said mass spectrometer;
• an ionization chamber and means defining an inlet passage through which a gas sample is introduced into said ionization chamber;
• inlet control means responsive to the pressure condition within said ionization chamber for controlling the volume of gas sample introduced into said ionization chamber;
• means for introducing electrons into said ionization chamber whereby the electrons bombard the gas sample thus forming ions within said ionization chamber;
• a filter chamber associated with said ionization chamber and into which a portion of ions and electrons generated in said ionization chamber are allowed to pass;
• a filter apparatus in said filter chamber operative to permit a stream of ions with a pre-selected mass-to-charge ratio to pass through said filter apparatus and ions other than those having the pre-selected mass-to-charge ratio being separated from the stream of ions;
• means for directing electrons toward ions other than those having the pre-selected mass-to-charge ratio in the area of said quadrupole filter so that the electrons combine with the ions;
• and
• means for sensing the ions passing through said filter apparatus and operative to generate a signal corresponding to the ion condition thereby detected.

A method of analyzing a gas sample in a mass spectrometer comprising the steps of:

• ionizing a gas sample in an ionization chamber by bombardment of said gas sample by electrons;
• migrating the ions from said ionization chamber toward a sensing mechanism;
• separating the ions on the basis of their mass-to-charge ratio prior to arrival of the ions at said sensing mechanism to allow only ions of a preselected mass-to-charge ratio to migrate to said sensing mechanism;
• calculating the proportion of the ions with the preselected mass-to-charge ratio in the gas sample based upon the amount ions that migrate to said sensing mechanism;
• migrating electrons along with said ions from said ionization chamber toward said sensing mechanism;
• and
• neutralizing the ions other than those of said preselected mass-to-charge ratio by allowing the electrons to combine with said ions prior to said sensing mechanism so that the sensitivity and operational integrity of the gas sample analysis is maintained on a continuous basis.

A method of neutralizing a mass spectrometer filter of undesired ions comprising the steps of:

• introducing electrons into an ionization chamber;
• creating an electric bias downstream of said ionization chamber to influence migration of said electrons into a filter chamber;
• and
• focusing the electrons toward the undesired ions in said filter chamber to be neutralized thereby allowing the electrons to combine with the ions thus neutralizing the ions.